1. Field of the Invention
This invention relates to a device for facilitating and simplifying the adjustment of resonators of an answering device coupled to a high frequency line for a microwave transmission system for information assigned to railroad vehicles or distance points with several digits which are each provided with a separate frequency range with frequency locations within a periodic transmission frequency band for the characterizing of an alphanumeric symbol, which information is transmitted from an interrogation device as an interrogation signal and is received again selectively frequency modulated by the resonators of the interrogation device.
2. Description of the Prior Art
Answering devices are known in the art which have been developed for such transmission systems. In this connection one may refer to German Letters Patent 1,290,611 and the German published application 2,047,153. In this system for the characterization of an alphanumeric symbol, two-out-of-five frequencies are provided within a frequency range of the transmission frequency band for each digit of information. These two frequencies are, in each case, provided with resonance pulses which are created in resonators. Therefore, the answer signal of an answering device receives for each digit of the information to be transmitted two resonance pulses so that in the case of a twelve digit informaion, therefore, 24 resonance pulses are provided. During the assignment of the frequency range of the transmission frequency band, successive digits of an information may be assigned also in the transmission frequency band of subsequent frequency ranges.
Basically, an answering device comprises a horn antenna, a hollow conductor coupled thereto as a high frequency line, and a short circuit plane closing off the hollow conductor at the other end. For technical production reasons such an answering device can preferably be produced of two half shells, whereby at the uncut longitudinal sides of the hollow conductor at least as many coupled coaxial line resonators are cast as there are digits in the information to be transmitted. For interference free operation of the entire system, it is of considerable importance that the resonators have a slight attenuation and are optimally coupled, with respect to oscillations, to the electromagnetic field in the hollow conductor. Slight attenuation of the resonators can generally also be achieved by a large dimensions of the resonator interior, which means its diameter should be chosen as large as possible.
In the interest of miniaturization, the hollow conductor should also be as short as possible, whereby there are only a few possibilities for the selection of the arrangement of the resonators at the hollow conductor. The distance of a resonator from the short circuit plane of the hollow conductor is basically prescribed by the position of its resonant frequency within the transmission frequency band. Each resonator should, if possible, have a distance to the short circuit plane which corresponds to a quarter or an uneven multiple of a quarter of the wave length of its resonant frequency. In such an optimum coupling of the resonators to the hollow conductor, and during the assignment of subsequent digits of the information to frequency ranges following each other in the transmission frequency band, the individual digits of the information respectively assigned resonators at the hollow conductor are secondary in such a way that during the adjustment of the resonators errors occur easily due to the confusing arrangement.